EDIT: Version 2020.2.12 has fixed the issue. Thanks =)
I just tested this with the new version you posted 2020.2.11 and the bug is still there.
You can test this by doing the following.
Create a plex server. and create a movie or tv show library.
Add your Mega.nz folder containing your media to it. (From your mounted Mega.nz drive)
Upload a new media file to Mega.nz to your media folder.
Have plex rescan the library for new media.
Plex will not pick up new media.
If you actually manually goto the mounted drive in windows explorer and open up the media folder it refreshes. You can at this point have plex rescan the library and it will pick up new media.
Again Google works perfectly fine seems to be tied to the Mega.nz drive.